Silencer with a plurality of resonance chambers

ABSTRACT

The invention relates to a sound absorber mounted on or in a component, wherein a sound which is to be absorbed is propagated. The silencer comprises a hollow body, which communicates with the component or forms a component part of the component. A plurality of Helmholtz resonators which operate in a parallel manner are arranged behind each other in the axial direction of the hollow body in at least one axial part of the hollow body.

[0001] The invention relates to a sound absorber on or in a component, in which sound to be absorbed, in particular, airborne sound, is dispersed.

[0002] Sound absorbers, or mufflers, are used in internal combustion engines, for example, for reducing noise emissions into the surrounding environment. For example, mufflers are arranged in an exhaust tract of an internal combustion engine, in order to lessen the sound produced and dispersed from the internal combustion engine. Likewise, in motor vehicles, sound absorbers are used in the fresh air tract of the internal combustion engine, in order, for example, to lessen the sound produced by an exhaust turbocharger in an engine utilizing such a turbocharger and to lessen the sound dispersed in the fresh air tract.

[0003] For damping sound which is dispersed in a line, so-called “shunt resonators” or “Helmholtz resonators” are known. Such a Helmholtz resonator essentially comprises a hollow chamber, which communicates with the interior of a line via a connection opening, in which the sound to be damped disperses, whereby the remainder of hollow chamber is closed. The gas volume enclosed in the hollow chamber operates thereby as a “spring” and the gas volume in the connection opening operates as a “mass”, whereby a vibratory system is formed. This vibration system can be stimulated into vibration by means of sound waves, whereby the sound wave energy is canceled, that is, the sound is damped. The damping effect of such a Helmholtz resonator, however, is limited to a predetermined frequency or to a predetermined frequency band. The frequency or frequency band with which the Helmholtz resonator utilizes its damping effect depends, for example, on the geometry, the cross section, the length, and therefore, the volume of the hollow chamber, as well as the connection opening of the Helmholtz resonator. A Helmholtz resonator, then, can best utilize its damping action if it is positioned on the line, such that its connection opening communicates accurately with the interior of the line there, where an antinode of a vertical sound wave of that frequency has formed, which is to be damped by the Helmholtz resonator. By the geometry of the line in which the sound is dispersed, any positions are provided in which a vertical sound wave can form. The exact position of an antinode can be calculated with predetermined frequency. In order to achieve an optimal damping of a predetermined frequency, then, the Helmholtz resonator must be connected as precisely as possible to the calculated position on the line. In the frame of large-volume manufacturing, such as for example, with the production of motor vehicles or motor vehicle components, generally the precise adherence of a desired mounting position can be ensured only with a relatively high expenditure. In addition, the band width of the frequency to be damped by the sound absorber equipped with a common Helmholtz resonator is very narrow, so that only peaks of a level of a predetermined frequency can be absorbed.

[0004] The present invention is concerned with the problem of providing an embodiment for a sound absorber of the above-described type, which can be relatively easily mounted and/or can be integrated, and thereby enables a high quenching action. In addition, a sound absorber should be provided, which has an improved quenching action and, in particular, has an increased broad-band action. In addition, the sound absorber should be able to be manufactured in a particularly cost-effective manner.

[0005] This problem is solved according to the sound absorber of the present invention with the features of claim 1.

[0006] The invention relates to the general idea of equipping a sound absorber with multiple, in particular, with a plurality of Helmholtz resonators, which are arranged side by side and operate their sound-absorbing action parallel to one another. By the arrangement of the Helmholtz resonators in the sound dispersion direction one after another, the precise positioning of the sound absorber on or in the component, for example, a line in which the sound to be damped is dispersed, does not occur, since of the multiple Helmholtz resonators, at least one is positioned near or directly on an antinode. Therefore, since no particularly precise mounting tolerances must be complied with, serial manufacturing or serial fitting of a component with the sound absorber of the present invention is facilitated.

[0007] In addition, it has been shown that the sound absorber equipped with multiple, parallel acting Helmholtz resonators utilizes a relatively broad-banded damping action, so that the sound absorber of the present invention offers altogether an improved damping action. This broad-band action provides, in particular, a wanted or tolerated irregularity of the individual Helmholtz resonators, which is provided with their manufacture.

[0008] Of particular advantage is an embodiment, in which in an axial section of a hollow body of the sound absorber in a zone extending in the axial direction and in the circumferential direction of the hollow body, multiple, parallel-acting Helmholtz resonators are arranged one after another, or consecutively, in the axial direction and side by side in the circumferential direction. In this manner, an areal arrangement of a plurality of Helmholtz resonators on the hollow body is provided, whereby the damping action or the broad-banded feature additionally is increased.

[0009] A compact structure is provided, then, when adjacent Helmholtz resonators border one another. One embodiment, in which the adjacently bordering Helmholtz resonators have common walls or common wall sections, is advantageous. In this manner, the manufacture of the Helmholtz resonators is simplified.

[0010] Of particular advantage is an embodiment, in which the cross sections of the Helmholtz resonators are smaller compared to the cross section of the hollow body. In this manner, one embodiment is formed, which can be used also with relatively minimal structural space because of its compactness. In this regard, it has been shown that the Helmholtz resonators, based on their large number and in spite of their minimal dimensions, affect a relatively large damping action, so that the sound absorber of the present invention, compared to a common sound absorber, is built to be smaller, thereby using a sufficient damping action with greater band widths. In particular, for high or higher frequencies, for example, approximately 900 Hz, a large damping value can be achieved with a small sound absorber.

[0011] In order to improve the damping action, in particular, the broad-band action of the sound absorber of the present invention, at least some of the Helmholtz resonators can differ from one another in different lengths and/or cross sections and/or geometries and/or orientations of their hollow chambers and/or in their connection openings.

[0012] Particular applications and uses of the sound absorber of the present invention are provided in claims 22 through 24.

[0013] Further important features and advantages of the invention are provided in the dependent claims, from the drawings, and from the associated description with reference to the drawings.

[0014] It is understood that the previously named features and those features to be described below can be used not only in the combination provided, but also in other combinations or alone, without departing from the frame of the present invention.

[0015] Preferred embodiments of the invention are shown in the drawings and will be described in greater detail in the following description. Although the following embodiments explain a particular use of the sound absorber of the present invention with an internal combustion engine, it is clear that this occurs without limitation of the generality of the present invention. In particular, the sound absorber of the present invention can be used always when airborne sound is produced or transmitted in an apparatus. In this regard, the sound absorber of the present invention is suited in particular for use in or on small apparatuses for damping high or higher frequencies, in particular, from 900 Hz, based on its compact structure. For example, the sound absorber of the present invention can be used with household apparatuses, for example, washing machines, dish washers, hair dryers, vacuum cleaners, or extractor hoods. Likewise, use with electrically motorized or compressed-air operated tools is possible, which work, in particular, with high engine speed. In addition, the sound absorber of the present invention can be used with exhaust air blowers, cooling blowers, air intake assemblies, air conditioners, and computers, in order to damp the frequencies determined there.

[0016] In the drawings:

[0017]FIG. 1 shows a schematic diagram-type principle illustration of an internal combustion engine, which is equipped with a sound absorber of the present invention;

[0018]FIG. 2 shows a longitudinal section through a sound absorber of the present invention;

[0019]FIG. 3 shows a cross section through a sound absorber of the present invention; and

[0020]FIG. 4 shows a cross section as in FIG. 3, however, with a different embodiment.

[0021] According to FIG. 2, a sound absorber 1 can be used with an internal combustion engine 2, in order to dampen sound there, which is produced essentially from an exhaust turbocharger 3 of the combustion engine 2. The sound absorber, or muffler, 1 is arranged for this purpose in a fresh air tract 4 downstream of an air filter 5 and upstream of a compressor 6 of the exhaust turbocharger 3. In this regard, the sound absorber 1 is built into a component, namely, a line 7 of the fresh air tract 4, is flowed-through by the air transported through the fresh air tract 4 and in this respect, forms an element of the line 7. The sound produced from the exhaust turbocharger 3 spreads through the line 7, against the flow direction and—without a sound absorber 1—would be moved relatively undamped to the air filter 5 and finally dispersed into the surrounding environment. By integrating the sound absorber 1 into the line 7, the determined frequency or frequency bands with reference to sound dispersed in the line 7 can be damped, whereby the sound emission of the entire assembly can be reduced. Preferably, the sound absorber 1 is positioned as close as possible to the sound source whose sounds are to be damped, that is, here, near the exhaust turbocharger 3. In the embodiment shown, the sound absorber 1 is arranged on the clean air side, that is, downstream of the air filter 5; likewise, an arrangement on the crude-air side is also possible.

[0022] Preferably, the arrangement shown in FIG. 1 is located in a motor vehicle again, which contains an internal combustion engine as a driving engine. Likewise, the invention can be used on stationary internal combustion engines 2. With the embodiment shown here, essentially the higher-frequency sound at least in selected frequencies produced from the exhaust turbocharger 3 can be damped. Likewise, for example, it is also possible with an internal combustion engine without an exhaust turbocharger to dampen sound produced by the internal combustion engine or elements thereof, for example, from valves of the combustion engine 2.

[0023] According to FIG. 2, the sound absorber of the present invention 1 has a tube-shaped hollow body 8, which forms a component of the line 7, in which the sound absorber 1 is installed or integrated. The hollow body 8 can be cylindrically formed, as shown here. Other forms, for example, with a cone-shaped hollow body, are likewise possible.

[0024] In an axial section 9 of the hollow body 8, characterized by a brace, which extends here along the entire hollow body 8, a plurality of Helmholtz resonators 10 are arranged in an outer side of the hollow body 8 one after another in the axial direction and side by side in the circumferential direction. Each of these Helmholtz resonators 10 has a hollow chamber 11, and each of these hollow chambers 11 communicates via an individual connection opening 12 with an interior 13 of the hollow body 8. Generally, the hollow chambers 11 of the Helmholtz resonators 10 are closed. By the chosen arrangement of the Helmholtz resonators 10, these act simultaneously and thus parallel together with the interior 13 of the hollow chamber 8 or the line 7. It is noteworthy that the individual Helmholtz resonators 10 are dimensioned relatively small compared with the line 7, since the cross sections of the Helmholtz resonators 10 or the hollow chambers 11 are small in comparison to the cross section of the line 7 or the hollow body 8. Nevertheless, the sound absorber 1 of the present invention can display a relatively strong damping action, in particular, with higher frequencies, for example, from 900 Hz, which is attributed to the large number of the individual, parallel-acting Helmholtz resonators 10.

[0025] According to FIG. 3, two zones 14 can be formed in the axial section 9 of the hollow body 8, in which, respectively, Helmholtz resonators 10 are formed one after another and side by side. In this regard, these zones 14 extend only partially along the circumference of the hollow body 8 and are arranged opposite one another on the hollow body 8, according to FIG. 3. In contrast, according to the embodiments of FIGS. 2 and 4, also a single zone 14 can be formed, which extends along the entire circumference of the hollow body 8 and completely encloses this in the circumferential direction. Accordingly, also the Helmholtz resonators 10 are arranged along the entire circumference side by side on the hollow body 8. Other embodiments also can have more than two such zones 14.

[0026] While with the embodiment of FIG. 3, the Helmholtz resonators 10 or their hollow chambers 11 and connection openings 12 are oriented parallel to one another, FIG. 4 shows an embodiment, in which the Helmholtz resonators 10 or their hollow chambers 11 and connection openings 12 are oriented radial to a longitudinal axis 15 of the hollow body 8.

[0027] With the embodiments shown, adjacent Helmholtz resonators 10 border one another. In addition, the bordering Helmholtz resonators 10 have common walls or wall sections 16, whereby their manufacture is simplified. In this regard, the hollow chambers 11 of the Helmholtz resonators 10 basically can have any cross section. However, circular, rectangular, or hexagonal cross sections are preferred.

[0028] At least some of the Helmholtz resonators 10 can differ from one another, in that their hollow chambers 11 and/or their connection openings 12 have different lengths and/or cross sections and/or geometries and/or orientations. In this regard, the damping performance, in particular, the broad band action, of the sound absorber 1 can be affected.

[0029] According to FIGS. 3 and 4, the hollow body 8 has a circular cross section. It is clear that the hollow body 8 can have basically any cross section, at least in the area of its axial section 9, in particular, a rectangular or polygonal cross section.

[0030] According to FIG. 2, an embodiment is preferred, in which at least in the axial direction of the hollow body 8, a distance 17 between the connection openings 12 of two adjacent Helmholtz resonators 10 is smaller than an entire or half wavelength of a frequency to be damped or smaller than a whole or half middle wavelength of a frequency band to be damped. By this manner of construction, with the mounting of the sound absorber 1 of the present invention, a precise positioning of the sound absorber 1 on or in the line 7 is attained. As long as the axial section 9 equipped with the Helmholtz resonators 10 is positioned in the area of a antinode, at least one of the Helmholtz resonators 10 is found relatively close or exactly at the maximum of the antinode. In this manner, an optimal damping action for the sound absorber 1 always can be permitted.

[0031] With a preferred embodiment, the sound absorber 1 of the present invention can be constructed, such that the hollow chambers 11 of at least some of the Helmholtz resonators 10 are formed in a common block, which, for example, has a “honeycomb structure”. This block, then, forms a separately manufacturable component, which can be attached to a wall section of the hollow body 8. This wall section includes the connection openings 12. By means of a suitable placement of the block on the wall section provided for this purpose, each hollow chamber 11 is associated with a separate connection opening 12. The wall section therefore defines the block radially inward. Radially outward, the block is defined, for example, by a common cover, which closes the hollow chambers 11 radially outward. For example, the two zones 14 in the embodiment of FIG. 3 each can be formed in this manner. In this manner, a type of housing can be formed on the hollow body 8, in which the separately manufactured block containing the hollow chamber 11 can be inserted. By closing this housing with a suitable cover, simultaneously, the hollow chambers 1 are closed radially outward. The block can be connected with the wall section of the hollow body 8 and/or with the cover in a suitable manner, in particular, welded.

[0032] The component, in which the sound to be damped disperses, is formed in the described embodiment by the line 7. Likewise, other embodiments are possible, in which the component, in which the sound to be damped disperses, is formed by another element of the fresh air tract, for example, by the air filter 5 of by a fresh air accumulator 18, from which the fresh air is distributed to the individual cylinders of the internal combustion engine (compare FIG. 1). Preferably, then, the hollow body of the sound absorber forms a housing or an element, for example, a housing wall, of the component. For example, the sound absorber of the present invention can be formed on or in the cover of an air filter 5. Basically, the sound absorber can be formed as an attachment part or as a mounting part. Likewise, it is possible to form the sound absorber as an integral element of the respective component. For example, the sound absorber is integrated in the housing of the air filter 5 of the air accumulator 8. 

1. A sound absorber on or in a component (7), in which a sound to be damped disperses, with a hollow body (8), which communicates with the component (7) or forms an element of the component (7), whereby at least in one axial section (9) of the hollow body (8), multiple, parallel acting Helmholtz resonators (10) are arranged one after another in an axial direction of the hollow body (8).
 2. The sound absorber according to claim 1, characterized in that in the at least one axial section (9) of the hollow body (8), multiple, parallel acting Helmholtz resonators (10) are arranged side by side in a circumferential direction of the hollow body (8).
 3. The sound absorber according to claim 2, characterized in that in the at least one axial section (9) of the hollow body (8) in a zone (14) extending in an axial direction and in a circumferential direction of the hollow body (8), multiple, parallel acting Helmholtz resonators (10) are arranged in the axial direction of the hollow body (8) one after another and side by side in the circumferential direction of the hollow body (8).
 4. The sound absorber according to claim 3, characterized in that the zone (14) encloses the hollow body (8) completely in the circumferential direction.
 5. The sound absorber according to claim 3, characterized in that two or more zones (14) are distributed on the hollow body (8).
 6. The sound absorber according to one of claims 1 through 5, characterized in that adjacent Helmholtz resonators (10) border one another.
 7. The sound absorber according to claim 6, characterized in that Helmholtz resonators (10) bordering one another have common walls or wall sections (10).
 8. The sound absorber according to one of claims 1 through 7, characterized in that the cross sections of the Helmholtz resonators (10) are smaller than the cross section of the hollow body (8).
 9. The sound absorber according to one of claims 1 through 8, characterized in that each Helmholtz resonator (10) has a hollow chamber (11), which communicates with an interior (13) of the hollow body (8) via a separate connection opening (12).
 10. The sound absorber according to claim 9, characterized in that a distance (17) between Helmholtz resonators (10) adjacent to the connection openings (12) is smaller than a wavelength or half a wavelength of a frequency to be damped or smaller than a middle wave length or half a middle wavelength of a frequency band to be damped.
 11. The sound absorber according to one of claims 1 through 10, characterized in that each Helmholtz resonator (10) has a hollow chamber (11), whereby the hollow chambers (11) of multiple Helmholtz resonators (10) are closed radially outward with a common cover.
 12. The sound absorber accordion one of claims 1 through 11, characterized in that at least some of the Helmholtz resonators (10) differ from one another in by having different lengths and/or cross sections and/or geometries and/or orientations of their hollow chambers (11) and/or their connection openings.
 13. The sound absorber according to one of claims 1 through 12, characterized in that at least some of the Helmholtz resonators (10) are arranged parallel to one another.
 14. The sound absorber according to one of claims 1 through 13, characterized in that at least some of the Helmholtz resonators (10) are arranged radially to a longitudinal axis (15) of the hollow body (8).
 15. The sound absorber according to one of claims 1 through 14, characterized in that at least some of the Helmholtz resonators are formed on the hollow body (8), such that a common block containing the hollow chambers (11) of these Helmholtz resonators (10) is bordered radially outward by a common cover and radially inward by a common wall section of the hollow body (8) containing the connection openings (12) of these Helmholtz resonators (10).
 16. The sound absorber according to claim 15, characterized in that the block has a honeycomb structure.
 17. The sound absorber according to one of claims 1 through 16, characterized in that the hollow body (8) forms a housing or a housing element of the component (7).
 18. The sound absorber according to one of claims 1 through 17, characterized in that the sound absorber (1) is formed as an attaching part for attachment to the component (7) or as a mounting part for installation in the component (7) or as an integrated element of the component (7).
 19. The sound absorber according to one of claims 1 through 18, characterized in that the component (7) forms an element of a fresh air tract (4) or an exhaust tract of an internal combustion engine (2).
 20. The sound absorber according to claim 19, characterized in that the sound absorber (1) is arranged in the fresh air tract (4) downstream of an air filter (5) and upstream of an exhaust turbocharger (3) of the internal combustion engine.
 21. The sound absorber according to claim 19 or 20, characterized in that the component is formed by a line (7) or an air filter or an air accumulator.
 22. A use of a sound absorber (1) according to one of claims 1 through 21 on or in an apparatus, which is operated by a combustion engine or with an electric engine or with compressed air.
 23. The use according to claim 22, characterized in that the apparatus is formed as a motor vehicle or a washing machine or a dish washer or a clothes dryer or a hair dryer or a vacuum cleaner or an exhaust air blower or an air intake assembly or a compressed-air-or electrical motor-operated tool.
 24. The use of a sound absorber (1) according to one of claims 1 through 21 for damping sound in the range of relatively high frequencies, for example, from approximately 900 Hz. 